1. Field of the Invention
The present invention relates in general to automotive air conditioning systems and more particularly to computer-controlled automotive air conditioning systems. More specifically, the present invention is concerned with computer-controlled automotive air conditioning systems of a type which uses a fuzzy system theory for controlling the operation of the system.
2. Description of the Prior art
Hitherto, various types of computer-controlled air conditioning systems have been proposed and put into practical use particularly in the field of motor vehicles. Such conventional automotive air conditioning systems are almost of a type which uses a computer operated on PID control (viz., Proportional plus Integral plus Derivative Control).
In order to clarify the task of the present invention, one conventional computer-controlled automotive air conditioning system of such PID control will be described in brief with reference to FIG. 63 of the accompanying drawings.
Referring to FIG. 63 of the accompanying drawings, there is schematically shown a control system of the conventional automotive air conditioning system, which is arranged to control the output power of an electric air blower 25 in accordance with information signals issued from various sensors and control switches. The air blower 25 is used for blowing a temperature-controlled air into the passenger room from an air conditioning unit.
In FIG. 63, denoted by numeral 1 is a switch "A/C" for energizing an air conditioning unit of the system, and denoted by numeral 2 is a switch "AUTO" for forcing the air conditioning unit to assume an automatic mode. Denoted by numeral 3 is a temperature sensor for detecting the temperature of the engine cooling water, and denoted by numeral 4 is a sensor "PBR" for detecting a pivot angle of an air-mix door. The air mix-door is pivotally installed in an air-mix chamber in which cold air and hot air are introduced. Thus, when the pivot angle of the air mix-door varies, the mixing rate of the hot and cold air changes thereby changing the temperature of the mixed air discharged from the air-mix chamber. Denoted by numeral 5 is a solar radiation sensor for sensing the quantity of solar radiation pouring on the vehicle body. Denoted by numeral 6 is an outside temperature sensor which senses the temperature of the surrounding air, and denoted by numeral 7 is an inside temperature sensor which senses the temperature of air in the passenger room. Denoted by numeral 8 is a blower speed control switch which, when manually handled, can fix the rotation speed of the blower motor 25 at a desired given level. Denoted by numeral 9 is a mode selection switch which selects the mode of the automatic air conditioning. More specifically, when the mode selection switch 9 is manipulated, air blowing apertures exposed to the passenger room are selected. Denoted by numeral 10 is a temperature setter switch which is manipulated by the passengers when they wish to change the room temperature.
Signals issued by the above-mentioned various sensor means 1 to 10 are introduced into a control unit 15 which comprises an input signal processing part 16, a temperature setting part 7, a temperature signal correction part 18, a microcomputer 19 and an output signal processing part 20. The signals from the sensor means 1 to 9 are fed to the input signal processing part 16, and the signal from the temperature setter switch 10 is fed to the temperature setting part 17. The signal outputted from the temperature setting part 17 is corrected by the temperature signal correcting part 18. By analyzing signals from the input signal processing part 16 and the temperature signal correction part 18, the microcomputer 19 outputs to the output signal processing part 20 a signal representative of a voltage suitable for operating the electric air blower 25. Upon receiving the signal from the microcomputer 19, the output signal processing part 20 outputs a switching signal for a transistor 22 and a control signal for another transistor 23. The voltage actually applied to the electric air blower 25 is controlled by these two transistors 22 and 23. That is, when the transistor 22 is switched ON, a relay 24 assumes ON condition. Under this condition, the electric air blower 25 runs at a high speed. While, when, with the transistor 22 being kept OFF, the other transistor 23 is in operation, the voltage actually applied to the electric air blower 25 varies in accordance with a voltage applied to the base of the transistor 23 by the output signal processing part 20. Accordingly, under this condition, the rotation speed of the blower 25 varies in accordance with the voltage of the base.
However, due to its inherent construction, the above-mentioned computer-controlled automotive air conditioning system has the following drawbacks.
(1) It is difficult to precisely control the rotation speed of the electric air blower 25 in accordance with a change in the environment which surrounds the vehicle. In fact, even when the environment of the vehicle changes, the rotation speed of the blower 25 is kept unchanged so long as the air-mix door keeps the same angular position.
(2) In the above-mentioned type of the air conditioning system, it tends to occur that the control of the system is oversensitive to the quantity of solar radiation. That is, in such type, each time the vehicle runs into or from the shadows of trees and clouds, the control mode is forced to meaninglessly change.
(3) In a type wherein a delayed control takes place when the temperature of the outside air is rising, such control may take place when the vehicle runs down from a higher place of lower temperature to a lower place of higher temperature. Of course, such delayed control is not necessary under such down-hill cruising.
(4) It is difficult to control the air conditioning system in accordance with the sensitivity or feeling possessed by the passengers. That is, in summer, it is preferable to make the fluctuation of the room temperature smaller than in winter upon changing a target room temperature, because in summer the passengers are thinly dressed and thus much sensitive to the temperature. However, the conventional control can not deal with this preferability.
(5) In a type wherein an intake door is installed in an outside air induction passage for varying the amount of outside air fed to the passenger room in accordance with an instruction from the computer 19, tuning of the intake door is difficult. If the tuning is improperly made, undesired "cycling" phenomenon tends to occur. That is, in such case, switching between outside air induction mode and inside air induction mode is overly and meaninglessly repeated.
(6) In the type wherein the temperature of air blown into the passenger room is controlled using the quantity of solar radiation as a control parameter, it is usual to determine the target temperature of the air blown into the passenger room by linearly processing the quantity of solar radiation. However, this linear processing tends to cause the temperature actually provided in the passenger room to differ from the temperature to which the feeling of passengers matches. That is, to a passenger who can easily bear coolness, it is preferable to allow the temperature control of the air blowing to be somewhat largely affected by the quantity of solar radiation, and at the time when in winter the passenger room is warmed, it is also preferable to allow the temperature control of the blown air to be largely affected by the quantity of solar radiation for protecting the passengers from having a rush of blood to the head. However, the conventional control can not deal with such preferability.
(7) In a type wherein the control of the air conditioning system uses as one parameter the temperature sensed by a temperature sensor installed in an aspirator duct through which the air in the passenger room flows back to the air conditioning unit, it tends to occur that due to the thermal capacity possessed by the aspirator duct the temperature sensor fails to make a prompt reply to a temperature change of the air which is flowing in the aspirator duct. That is, it takes a little time until the temperature sensor issues a signal which represents the exact temperature of the air. This causes a delayed control of the air conditioning system.